This was an interesting one. Personally, I would never say "tell about," and I've never heard anyone say it, either. That said, I can understand it in the context of a text book or exercise, when the book writers might not want to say "tell us about" or "tell me about," because that would be even more awkward.

Oh, and I'm from New York (but have also lived in Boston and Madison, WI), since some folks brought up potential regional differences.